In-cylinder direct injection type engines, each of which directly injects fuel into cylinders, are widely known. For example, Japanese Unexamined Patent Application Publication No. 2009-47055 (PTL 1) is disclosed. The regulations on emission and fuel efficiency are strengthened in recent years, and consequently such in-cylinder direct injection type engines require more accurate engine control. For example, in the above-described publication, the fuel injection timing is set according to the concentration of alcohol in composite fuel.
In general, the combustion of an internal combustion engine is influenced by not only the alcohol concentration but also various kinds of environmental conditions. In particular, the temperature of fuel exerts an influence on a vaporization rate of fuel spray, the temperature of in-cylinder air-fuel mixture, and the like. Fuel that is supplied into an engine cylinder is heated by heat transferred from a fuel rail and a fuel injection valve. In particular, in the case of in-cylinder direct injection type engines, heat generated by the combustion causes the temperature of a fuel injection valve to become high. Therefore, the fuel temperature measured when the fuel is supplied to the cylinder is considerably higher than the fuel temperature measured at the time of fuel-pump discharging. In addition, in the case of multicylinder engines, dispersion in combustion on a cylinder basis, the temperature distribution of an engine block, and the like cause a difference in fuel temperature among cylinders. Therefore, in order to increase the emission performance, the fuel efficiency performance, the output performance and the like, it is important to detect a difference in fuel temperature among cylinders, and then to control the engine according to the difference.
Japanese Unexamined Patent Application Publication No. 2014-118952 (PTL 2) discloses a means for measuring the temperature of fuel injected into cylinders. A fuel injection device in this publication is provided with a temperature sensor for measuring the temperature of fuel in the upstream of a sheet part in a nozzle body.